feat(docs): document WithPolicyFrom re-wrap helper

[marythought]

Summary

Adds a tdf.mdx section for sdk.WithPolicyFrom, a new TDFOption builder that binds the source TDF's policy — its attribute value FQNs — to a new TDF being created. Targets re-wrap pipelines where the source policy should carry forward without callers handling the manifest's base64 + JSON encoding themselves.

Call site is a single line, matching the existing With* option-builder idiom:

if ok, _ := sdk.IsValidTdf(file); !ok {
    return // pass through unchanged
}
reader, err := client.LoadTDF(file)
if err != nil {
    return err
}
_, err = client.CreateTDF(out, transformed, sdk.WithPolicyFrom(reader))

Reader.Init is not required — DataAttributes reads the policy from the manifest, which LoadTDF has already populated.

Companion PR

Documents the function landing in opentdf/platform#3476. Draft until that PR merges — the example references a symbol that doesn't exist in the SDK yet.

How this was drafted

Generated by the docs-drift skill mining the function's godoc example block verbatim. No example code was invented; the snippet shown is exactly what the function's author wrote in the godoc.

Test plan

• Verify rendered output in Docusaurus preview
• Reviewer signs off on placement (currently in tdf.mdx after IsValidTdf, before BulkDecrypt)
• Mark ready for merge after feat(sdk): add WithPolicyFrom re-wrap helper platform#3476 lands

🤖 Generated with Claude Code

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 10d79aa4-3e71-4763-9845-0382dc27e219

📥 Commits

Reviewing files that changed from the base of the PR and between 5be45e2 and c6fc6c7.

📒 Files selected for processing (1)

• docs/sdks/tdf.mdx

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch demo/docs-drift-with-policy-from

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[gemini-code-assist]

Code Review

This pull request adds documentation for the WithPolicyFrom function in the Go SDK, which allows binding a source TDF's policy to a new TDF. Feedback was provided regarding an inconsistency in the documentation concerning the Init(ctx) requirement for Reader.DataAttributes. Additionally, the example code contains a logic error where a return statement is missing after a validation check, and the SDK client variable naming is inconsistent with the rest of the document.

[github-actions]

❌ Surge preview build failed — no preview was deployed. Check the workflow logs for details.

Once the build passes, the preview will be at: https://opentdf-docs-pr-323.surge.sh

Common cause: If the build failed on vendored YAML validation, run the following locally and commit the result:

npm run update-vendored-yaml
git add specs/
git commit -m "chore(deps): update vendored OpenAPI specs"

[github-actions]

❌ Surge preview build failed — no preview was deployed. Check the workflow logs for details.

Once the build passes, the preview will be at: https://opentdf-docs-pr-323.surge.sh

Common cause: If the build failed on vendored YAML validation, run the following locally and commit the result:

npm run update-vendored-yaml
git add specs/
git commit -m "chore(deps): update vendored OpenAPI specs"

[github-actions]

❌ Surge preview build failed — no preview was deployed. Check the workflow logs for details.

Once the build passes, the preview will be at: https://opentdf-docs-pr-323.surge.sh

Common cause: If the build failed on vendored YAML validation, run the following locally and commit the result:

npm run update-vendored-yaml
git add specs/
git commit -m "chore(deps): update vendored OpenAPI specs"